Agricultural Water Use in River basins : A Comparison between the Limpopo and the Indo-Gangetic – Cai X.L, Researcher – Water Resources & Remote sensing, International Water Management

Water for a food-secure world

Xueliang Cai, Bharat SharmaInternational Water Management Institute

Agricultural Water consumption in the Limpopo and the Indo-Gangetic Basins – A Quick Comparison

Water for a food-secure worldWater for a food-secure world

Is the comparison meaningful?

Yes, it isBasin perspective, powered by remote sensing, helps…

Limpopo Indo-GangeticGeographic Area (million ha): 41 225

Population (million): 14 747Annual precipitation: 530 1254

Cropland area (million ha): 2.3 114

Irrigated area (million ha): 0.24 62.1

Cropping pattern: Maize Rice-wheat

Water resources: Surface water Ground water and surface water

… and vast differences in social and economic situations…

Water for a food-secure worldWater for a food-secure world

MethodologyEvapotranspiration – key agricultural water consumption

Actual ET map

potential ET map

ETa – actual Evapotranspiration, mm.

ETf – evaporative fraction, unitless.

ET0 – Potential ET, mm.

Tx – Land Surface Temperature (LST) of pixel x from thermal data.

TH/TC – the LST of hottest/coldest pixels.

CH

xHf TT

TTET

fpa ETETET

SSEB

ET fraction map

MODIS LSTDaily weather station data

Crop dominance map

Water for a food-secure worldWater for a food-secure world

ET maps

Actual ET map of the Limpopo for the year 2005

Actual ET map of cropland areas in the IGB for the year 2005-06

Average Min Max SDV

Limpopo 779 88 1814 208

IGB 944 145 1629 222Unit: mm

Limpopo IGB

Water for a food-secure worldWater for a food-secure world

Factors affecting water consumption

ETa / rainfall

Crop water stress (ETa/ETp)

Higher ET at downstream areas and South African commercial irrigated areas

Higher ET in Indian Punjab and Haryana and downstream areas

Limpopo IGB

Water for a food-secure worldWater for a food-secure world

Factors affecting water consumption

ETa / rainfallLimpopo IGB

As opposed to the Limpopo basin, the IGB with extensive irrigation clearly showed the areas where ET exceeds precipitation and where not.

Water for a food-secure worldWater for a food-secure world

Factors affecting water consumption - IGB

Water for a food-secure worldWater for a food-secure world

Factors affecting water consumption - Limpopo

The temporal evolution of rainfall against ET at selected sites in the Limpopo basin

Water for a food-secure worldWater for a food-secure world

Improving water management to improve agricultural water productivity

IGB: targeting at bright spots? Is there enough water? Sustainability?

Limpopo: how to improve yields? Regulate water consumption at the right timing?

Water for a food-secure worldWater for a food-secure world

Thank you!